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412

SESAM£ OIL

above,  with carbon disulphide  and  sulphuric  acid.    Freshly prepared  and
dissolved in alcohol, it should have no acid reaction.

Castor oil for industrial purposes (soap-making) may have : moisture and
impurities up to i % ; D = o -960-0 -974 ; iodine number, 82-86 ; solidifying
point, — 10° to — 18° ; solidifying point of the fatty acids = 3° ; acetyl number
of the fatty acids = 153-4-156 ; Maumene number (Tortelli) = 67-8°.

SESAME OIL

From the seeds of Sesamum ind.ic.um and S. orientale, is more or less
deep yellow, of faint special odour and pleasant^taste. From 16 to 19
grams dissolve in 1000 c.c. of absolute alcohol at 15°. Its characters are
given in Table XLIV.

With Heydenreich's, Hauchecorne's, Brulle's and Bellier's reagents it
gives the colorations usual for seed oils. Characteristic of sesame oil is
the following colour reaction, which serves to detect it in olive oil and in
ah1 other oils and fats.

1.  Villavecchia and Fabris Reaction.1—Two or three drops of alco-
holic furfural solution (2 grams of furfural in 100 c.c. of 95% alcohol)2
and then 5-10 c.c. of the oil and 10 c.c. of pure cone, hydrochloric acid
(D I-IQ) are poured into a test-tube, the whole being well shaken for a few
moments and then left to stand.   The acid, coloured dark red, soon separates
in the lower part of the tube and becomes increasingly dark, while the upper
oily layer represents a yellowish-red emulsion.    The coloration is clearly
observable even with mixtures containing only 0-5% of sesam6 oil.

No other oil gives such a reaction ; only certain olive oils (from Tunis and
Algeria, and some from Bari, Brindisi and Lecce) may yield with the above
reagent a pink or reddish colour, which is, however, always less intense than
and quite different in tint from that produced by sesame oil. In doubtful cases,
the reaction may be carried out with the liquid fatty acids separated by Tortelli
and Ruggeri's method (see General Methods, 18, i).

2.  Detection of Adulterations.—Sesame" oil may be adulterated with
drying oils, colza oil and arachis oil: the first raise the iodine numbei and
the Maumene' number, while the others are detectable by testing for the
arachidic and lignoceric acids and by the Tortelli and Fortini test (see
Arachis Oil and Colza Oil).

*

* #

Comestible sesame oil should be clear, of normal taste and odour, and not
too acid (fresh oil may contain 0-5-5% °f free acids, calculated as oleic acid ;
old oils may contain as much as 35%).

The permissible limits for the industrial oil (for soap-making) are : moisture

1  This reaction (see Zeitschr. fur angew. Chemie, 1892, p. 509, and 1893, p. 505) is
due to the action of furfural, in presence of cone, hydrochloric acid, on the methylene
ether of   hydroxyhydroquin onecontained in sesam6 oil, according to the investiga-
tions of Malagnini and Armani (see Rend. Soc. chim. di Roma, 1907, V, p. 133).    It
serves as a rational substitute for Baudouin's reaction, which consisted in shaking the
oil with cone, hydrochloric acid and sugar.   In Baudouin's reagent also the active
principle is furfural, which is formed by the action of the acid on the saccharose, but,
this formation being slow and limited, Baudouin's reaction is less rapid and certain.

2  The furfural should be pure and recently distilled, so that it shows little colour.STOR   OIL